Electrical indicating target



Dec. 4, 195] Filed Aug. 8, 1945 F. E. M AVOY ELECTRICAL INDICATING TARGET 2 SHEETS-SHEET l INVENTOR fian/ZEMc/iuoy Patented Dec. 4, 1?51 CFFICE 2,576,960 ELECTRICAL INDICAT ING TARGET Frank E. McAvoy, Teaneck, N. 1., assignor to John Milton, Jr., as trustee Application August 8, 1945, Serial No. 609,633

4 Claims. (01. 273-1022) This invention relates to target shooting apparatus and more particularly to such apparatus for determining and indicating at a remote point the number of hits made on the target.

In target practice it is not only desirable to know when a target has been hit but also how many times it has been hit for a given number of rounds fired. In the past such target shooting results have been achieved by visual counting of the punctures in a target after a given period of shooting. Such a procedure is not only subject to inaccuracy but also entails considerable delay before the results of the shooting are known, and these disadvantages are accentuated with weapons of high fire power such as those which have been developed in the present era. For example, in practicing ground strafing with high fire power weapons from aircraft, especially at high altitudes, or from fast moving ground vehicles, the possible spread of the bullets is so great that all target attendants must be removed to great distances, e. g. thousands of yards, from the targets before firing may begin. Thus, the results of any particular shooting sequence cannot be known until these attendants have returned to the targets and counted the hits. This entails considerable delay with the attendant waste of manpower'and equipment; The present invention enables the hits made during such practice to be determined and registered instantly at any convenient point remote from the target so that the results of the shooting can be known to the marksman almost as soon as the bullets strike the target.

It is an object of this invention to provide an electrical target structure capable of producing a sharp change in an electrical circuit characteristic each time a bullet passes through the target. -It is a further object of this invention to provide apparatus to use these electrical changes-to actuate timingand indicating mechanisms at some remote point.

1 It is a further object of this invention to provide target shooting apparatus which instantly indicates when a target has been struck by a bullet and which is capable of determining, counting and indicating the number of such hits, and of rendering such indications at any desired point remote from the target.

.xAnother object of the present invention is to provide such target shooting apparatus which instantly indicates the number of shots registered on the target in any given period of time and which indicates this number accurately for all bullets which in flight touch any part of the target surface. a

These and other apparent objects and advantages of this invention are obtained by the means described in the following specification and may be more readily understood by reference to the accompanying drawings wherein:

Figure 1 shows a target structure in accordance with the present invention with portions broken away to show more clearly its internal structure,

Figure 2 is the schematic wiring diagram of a target shooting apparatus embodying the present invention arranged to count the number of hits on a target of the type shown in Figure 1.

A novel automatic hit-registering target in accordance with the present invention is shown in Figure 1 with successive layers shown cut away in one corner to more clearly show its multilayer construction. A suitably shaped sheet of hard-pressed cardboard, untempered Masonite or the like, forms the base of the target and is mounted on the two supporting bars 34 and 36. This cardboard 90 is covered with an electrode layer 92 of metal screening, thin metal sheet or the like, for example, 56 mesh screen of galvanized iron, which in turn is covered by a layer 94 of light air cell material as, for example,

a quarter of an inch layer of corrugated card-- board. On top of this air cell material is a thin layer 96 of hard material, for example, a sheet of hard fiber twenty thousandths of an inch thick, on top of which is placed another layer 98 of metallic screen material similar to layer 92. With the construction just described, when. a metallic bullet of a length greater than the thickness of layers 96 and 96, i. e. greater than one quarter of an inch, passes through the target for a moment, it contacts both screen 98 and screen 82, thus forming an electrical connection therebetween. If the electrodes of this target, 1. e. screens s2 and so are each connected to one line of an electrical circuit responsive to a short circuit between these lines, this circuit will react each time a bullet passes through the target. The thin hard surface layer 96 serves to prevent the wire screen 98 from being badly distorted so that it might form a permanent short-circuit connection to screen 92. The layer 96 of air cell material is provided to prevent the concussion waves in front of the bullet from bursting large holes in the back of the target and therefore in the second layer of screening 92. A layer of sim-' ilar material could be used for the backing-up base 90 of the target, but such a construction is not essential. If, in spite of the hard surface layer 96, wires from the first electrode layer 93 should become permanently connected to screen though several such bullets may pass through the same holes in the target so long as-they make even a brushing contact with an edge portion of the target on their way through; Further,

this novel target construction permits high speed electrical circuits to be used to determine. andindicate the hits made on the targets.

Figure 2 shows one embodiment of the invention in which the number of hits on a target may be-counted-and indicated through. a specialelectronic tube circuit by means f a suitable counter and indicator mechanism.

Referring to Figured, the two metal mesh electrode layers 32 and seer one of the novel targets, of the type described above and generally indicated at TA-I, are connected by conductors IIlI and IE2, respectively, through two sets of normally closed contacts I03 and I64 of a relay RY-I and leads I65 and I06, respectively, to the midpoint I6] of a voltage divider formed of two resistors R-I and R-Z connected in series to the grid G-I of an electronic tube V-I, of the grid c ontrolled gas-filledtype frequently referred to under the trade name Thyratron. The, voltage divider formedof resistors R-I and R-Z-is connected through two conductors I08 and l flfiacross the output terminals HO and H2 of a suitable direct current power supply, generally indicated at IIlIl. Such a power supply comprises a power transformer T-g-La rectifier tube V-Z, a filter choke F-I and a filter condenser. C-I.,connected in a full wave rectifier circuit in the; usual manner. The primary II4 of transformer T-I is connected through a line switch Sl to a suitable A. 0. power supply line II6. An indicator lamp L -I connected across, this transformer primary II to indicate when, the switch S- -I is closedand the circuit is energized. Thecathode K-I of the tube V-I is heated from a heater winding M8 on the transformerVT-I, and the midpoint of this winding H6 is connectedtoanintermediate point I26 on a voltage divider; formed of two resistors R-3 and R,4 also connected across the output terminals III] and I I2; f;the power supply line I60. The plate 3-1 of the tube v l is connected through asuitable counter indicator mechanism, generally indicated;,at I22 and hereinafter. to be. described in greater detail, and a resistor R-5 to the positive terminal III) of the power supply. The grid G-I,

of the, tube V- l, in addition to being connected to one, electrode 98 of the targetTA-I through contact W140i ,relay RY-I is also connectedto the .negative terminal N2 of the. power supply through\ a grid resistor R6 and to its cathode K-I through the intermediate point I of volt-. agewdivider R-3, R-4 through a gridcondenser (3-2.: The.v counter indicator mechanism I22,

shown schematically for purposes of clarity, in-

cludes a stepping electro-magnet M-I which moves an armature member I24 against the pull of a biasing spring I26 to move a pawl member I28-along the teeth of a circular ratchet member I30 mounted on a shaft I3I to move itone increment each time the electro-magnet M-I-isenergized. This rotates shaft I3l in steps against the pull of a spiral spring I32 surrounding the shaft. A circuit breaking switch S2 comprising two normally-closed contacts I2! and I29 is connected in series with the stepping magnet M-I to deenergize the magnet each time that it is energized to move the pawl I28 and thus rotate the ratchet I39 through one increment of its motion. To. accomplishithis, the contact I21 is arranged to project under a portion of the armature member I24 so that it is moved away from contact I29 as the armature I24 moves through the last part'of its motion. This switch is necessary. because. of. the well-known characteristics of the gridecontrolled, gas-filled tube V-I whereby, after a. suitable control potential is applied to its grid G-I'to cause the tube toionize and conduct current, it continues to conduct until its anode-cathode circuit is broken for sufiicient period of time to permit it todeionize. The-rotation of the shaft I3I causes it to move an indi-- cator pointer I34 along a graduated scale I36. In order to hold the ratchet I3t in the positions to which it is 'moved by the pawl I28 by each successive energizationof the electromiagnet M-I, a latch mechanism is provided comprising a piv-, oted arm I 38 carrying a tooth I46 which is held against the periphery of .the ratchet I30 by a. spring I42. This tooth I40 is shaped as shown in the drawing soas tolatchtheratchet I36 in any position to whichit is moved, thus preventing it from being returned to its initial position by the spiral spring. I32; A releaseor 'resetl' magnet M-2 is provided to release the latch I46 and permit the-indicator pointer I34 to return to its initial-orflzero position under the influence of the spiral spring I32 by attracting an armature member I44 secured to the lever I38. The release electro-magnet M-.2 is connected to the positive terminal lIil of the power supply through resistor R-5. and to the. negative tere minal H2 of the power-supply through a release or "reset switch 5-3 and a resistor R-I. The counter mechanism I22 is also provided with a limit switch S-4. comprising two normally open contacts I46.and I41 arranged to be operated by a. cam I48 mounted on the shaft I3I and so positioned thereon as to.close' the contacts I46 and I4'I-when the .indicator pointer I34 reaches the end of scale I36. A. condenser 0-3 is connected across the winding of electromagnet M-I to determine .its operating speed and aresistancecapacity filter circuit, comprising a condenser 0-4 and a resistor-R4; is connected across the circuit-breaking switch; 8 -2., The contacts I46 and I4! of the limit-switch S-4 are connected through conductors I59 and I52, respectively, in series with the solenoid. I54 of the relay RY-l across the power supplyline-IIE, Thus the relay RY-I is energized-and its contacts are moved to their alternate position when the pointer I34 of counter I22 reachestheupper end of its scale causing cam I48 to close the circuit between contacts I46 and Mlof-limitswitchS-fi. Energization of the relay RY-I disconnects the electrodes 92 and 98 of target TA-l from grid circuit of V-I and connects these electrodes, across the low voltage high current secondary I60 of a. transformer T-2 whose. primary I62 is connected across the. supply line. 6.; In additionto limit switch 84,. a switch 3-5 is provided also to operate relay RY-I when desired. An indicator lamp L-2-is connected across the winding I54 of mechanism just described now is apparent. A positive potential isap'plied to the plate P-I of the grid-controlled gas-filled tube V-I from terminal IIO of the power supply I00 through resistor R-5, electro-magnet M-I and switch 8-2 of counter I22. The values of the resistors R-3 and R4 in the voltage divider R-3, R-4 are so chosen that the potential of the intermediate point I20 is much closer to the potential of the negative terminal I I2 than to the potential of the positive terminal IIO of the power supply. For example, R-3 might have a value 25 times as great as R-4, i. e. R-3 might equal 25,000 ohms and R-4 equal 1,000 ohms. With such an arrangement, a large potential, positive with respect to its cathode K-I, is applied to the plate P-I of tube V-I and a small potential, negative with respect to its cathode K-I, is applied to the grid G-I of this tube. The values of the resistors R-I and R-2 of the voltage divider R-I, R-2 are so chosen thatthe intermediate point I 0'! is considerably more positive than the intermediate point I20 of voltage divider R-3, R-4, e. g. R-I might equal 50,000 ohms and R-2 equal 50,000 ohms.

The apparatus just described is made ready for operation by connecting it to the power supply line M0 by closure of switch S-I. At this time switch 8-3 should be open and the two electrodes 92 and 08 of the target TA-I will be connected through contacts I03, I04 of relay RY-I to the grid circuit of tube V-I because the winding I54 of relay RY-I is deenergized, the pointer I34 of the counter I22 being on zero. When a bullet passes through the target TA-I, it will cause a momentary short-circuit between electrodes 02 and 98 as above described. This momentarily connects the intermediate point I01 of the voltage divider R-I, 52-2 to the grid G-I or" the tube V-I, causing a potential to be applied thereto which is considerably more positive than the potential of the cathode K-I, i. e. the potential of the intermediate point I20 of the voltage divider R-3, R-4. This positive potential causes the gas-filled tube V-I to ionize and conduct current so that its anode-cathode current flows through circuit-breaking switch S-2 and the winding of electro-magnet M-I to energize this electro-magnet and thereby attract armature member I24 causing pawl I28 to pull the ratchet I30 through one increment of its rotation. At the same time, as it reaches the limit of its stroke, it strikes contact I2'I of limit switch S -2 to open the circuit between contacts I21 and H0, thus opening the anode-cathode circuit of tube V-I, causing it to deionize and become nonconductive once more. Because the application of the positive potential to the grid G-I of the tube V-I which causes it to ionize is only mementary, i. e. lasting only for the period during which the bullet bridges the gap between the two electrodes 92 and 98 of target TA-I, tube V-I will not ionize again until another positive pulse is applied to its grid G-I. This cycle of operations is repeated each time a bullet passes through the target TA-I so that the indicator pointer I34 is stepped ahead one increment for each hit made on the target. Thus its position along the scale I36 indicates the number of hits during any predetermined period of operation. Because of the high speed of operation of such a grid-controlled, gas-filled tube as V-I, it is possible to count thousands of hits per minute if desired, a feature which is highly advantageous today because of the great fire power of modern weapons.

During operation it is possible, as above mentioned, that the two electrodes 92 and 98 of the target TA-I may be permanently short-circuited by a piece of one of the electrodes bridging the gap to the other. Such an accident might occur if numerous bullets all passed through a small area of the target, and it would cause an incorrect indication of the number of hits on the target. To provide for such a contingency, transformer T-2 and relay RY-I are provided to permit such accidental short circuit to be burned away. When the relay RY-I is energized by passing a current through its winding I54, the electrodes 92 and 98 of the target TA-I are disconnected from the grid circuit of the tube V-I and connected across the secondary of transformer T-2 by means of the contacts I 50 and I58. This connects an electrical current source of high current and low voltage between the electrodes 02 and 98 sufi'icient to burn away any bridging portions of the electrodes. A limit switch 8-4, in the counter mechanism I22, is provided to automatically make this connection by energizing relay RY-I each time the indicator pointer I34 reaches the end of its scale I30. Thus, in the event that a short occurs between the electrodes 92 and 98 of the target, a positive potential will be applied continuously to the grid G-I of tube V-I, as above described, so that the pointer I34 will be automatically stepped rapidly to the end of its scale I36 to close limit switch S-4 and cause the shorting portions to be burned away. Operation of the limit switch S-4 also causes the indicator lamp L2 to be lighted to call the operators attention to the fact that the pointer I34 has reached the end of the scale I36 so that he can operate switch S3 to energize the reset electromagnet M-2 to cause the pointer I34 to be returned to its initial position under the influence of the spiral spring I32. If desired, another set of contacts, similar to contacts I46 and I4! of limit switch 8-4 may be provided to be operated by the cam I48, preferably slightly later than operation of switch 8-4, as a substitute for the manually operated switch S-3 to automatically return the pointer I34 to its initial position whenever it reaches the upper limit of its motion on scale I30. At the same time, the closure of such auxiliary contacts on switch S4 may operate a dial-type counter mechanism to indicate the number of times that the pointer I34 of the mechanism I22 moves through the length of its scale, thus permitting a totalized count in the event that the number of hits in the desired period of time exceeds the number of steps in the counter mechanism I22.

With a self-registering target mechanism of the type just described, it is possible to determine instantaneously the number of hits on targets made by high fire power modern weapons without endangering personnel; thus eliminating the need for discontinuing all target practice while men enter the target area to determine the number of hits by visual examination of the targets.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiments above set forth without departing from the scope thereof, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative only and not in a limiting sense.

I claim:

1. For use in target shooting apparatus. a tarpassing through the assemblage of 'layers and functioning as a support for the inner layer of conductive material as the projectile passes u h i s V 2. The targetof claim 1 in which the inner layer of electrical conductive material is metal screening. I I I,

3. In target-shooting apparatusfa target in Cluding at least two electrodes formed of spaced apart layers of electrically conductive material and adapted to be momentarily 'short' circuited by the passage of projectiles in flight through said target to produce electrical target-signals of short duration, substantially instantaneously 'operable target-signal amplifying means including a grid controlled gas-filled tube'having a grid electrode and plate and cathode electrodes,

means including an electrical conductor connected directly to said grid electrode'to impress signals thereupon corresponding to the targetsignals, circuit means for impressing apositive potential on said plate electrode, said tube being adapted to be actuated by said target-signals as received by the grid electrode, indicator means responsive to actuation of said tube to indicate the passage of one or more projectiles through said target, normally closed electrical switch means connected in said circuit means for'im pressing a positive potential on the plate electrode, and means responsive to firing of saidtube and to actuation of said indicator means for'momentarily opening said circuit means to deenergize and cut off said tube to'set up the system 8 to receive' fand record th e p'assa'ge or the next projectile through thetar'get. H V s 4. In target-shooting apparatus a target including at least two electrodes formed of spaced apart layersof lectrically conductive material and adapted to bemomentarily short -cir'cuited bythe passag'e of projectiles in flight through "said target to produce electrical target-signals be short duration, substantially instantaneously operable target-signal amplifying means comprising an electronic tube having a cathode and a controlling electrode, an input circuit connected to'said controlling electrode comprising continuous electrical connections between said target electrodes andfsaid' tube'controlling elec- 'trode] whereby said target signals are applied substantially simultaneously with their generation'fin'thetarget, said input circuit having a capacitor in parallel between the controlling electrode 'andthe cathode ofsaid electronic tube,

means for maintaining said tube in condition to respondto successive target signals, and an indicator responsive to change of conduction of said tube to indicate the passage of one or'inore projectiles through said target.

FRANK E. McAVOY.

REFERENCES" CITED The following references are of record in the file of this patent:

- UNITED sTATEs PATENTs Certificate of Correction Patent No. 2,576,960 December 4, 1951 FRANK E. McAVO Y It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 34, list of references cited, under UNITED STATES PATENTS for the patent number 479,109 read 474,109;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Olfice.

Signed and sealed this 18th day of March, A. D. 1952.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

